


Mists of the Otherworld

by DarthImperius



Category: Harry Potter - J. K. Rowling, Percy Jackson and the Olympians - Rick Riordan
Genre: Celtic Mythology & Folklore, Demigod Harry Potter, Gen, Mythology - Freeform
Language: English
Status: In-Progress
Published: 2020-04-16
Updated: 2020-04-16
Packaged: 2021-02-23 13:01:44
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,312
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23678518
Author URL: https://archiveofourown.org/users/DarthImperius/pseuds/DarthImperius
Summary: Upon running away from the Dursleys after the debacle involving Marge, Harry finds himself unexpectedly introduced to a new world after being attacked by the Minotaur. With a unknown divine heritage revealed, the young wizard must learn to navigate the Otherworld of old myths and survive the trials ahead.
Comments: 3
Kudos: 56





	Mists of the Otherworld

**Author's Note:**

> Disclaimer: Harry Potter belongs to J.K. Rowling, while the Percy Jackson & the Olympians series belongs to Rick Riordan.

* * *

**Author's Note:**

Okay, so a bit of an explanation first. The story is mainly centred in Britain, as such it features a set of British deities. Instead of using the real-life pantheons, I decided to create one instead, with its own backstory. The historical deities are still present however. Most of them, that is. For instance, the "Tuatha Dé Danann" of Irish mythology no longer exist, and their absence will be explained in the story. Keep in mind that the story of Percy Jackson and its characters will still appear.

I hope you enjoy this plot-bunny.

* * *

**Chapter 1 – The Minotaur and the Horseman**

The Dursleys were… tolerable at best.

Spending the summer with them was a chore that Harry would wish upon no one. Well, that was not really true, but that was not the point. The point was that the Vernon, Petunia, and Dudley Dursley were mildly tolerable.

Marge Dursley, on the other hand, was not.

It had been her presence and constant insults towards his parents that had let to Harry's current predicament. And Marge's as well, but she was now at least half- the size of her ego. Harry on the other hand, had used magic outside of Hogwarts, and even though it was unintentional, he was certain he would get in trouble for it.

Well, that and running away from his house at night. His luck was that Little Whinging was not a town considered to be troubled. Harry had found himself on the playground, and dragging his possessions with him, he headed towards a secluded and dimly lit section of the park, allowing him a bit of rest without being seen by anyone else. Hungry and tired, Harry had some Galleons in his pocket, but he was far away from London and Diagon Alley for them to be useful. He sat down on his trunk, and rested for a while, hoping that no one would find him there. Perhaps he could risk his luck and walk towards the centre of London? The city was relatively near, after all.

Grabbing his trunk and Hedwig's cage, Harry got up and walked out of the park and into the streets. Yet he only took a few steps before something made him stop. At the drive's end stood a looming figure, the lights of the street casting its shadow on the asphalt. No creature from the wizarding world, that much Harry knew. Or at least, he thought he knew. But he knew the thing from mythology. Everyone did.

Which led to the question – why was there a minotaur in Surrey? More importantly, why was it quickly running towards him?

No time for questions, Harry took out his wand and pointed it at the massive beast, and thought on the spells he had learnt in school.

" _Flipendo_!"

An orange beam of light shot towards the minotaur, hitting the creature in the chest and knocking it backwards. Yet the creature quickly recovered from the spell, and roared before it tried to charge at Harry once again.

" _Incendio_!"

Flames shot from the wand and set the fur of the minotaur on fire, further infuriating the beast but not halting its movement.

" _Diffindo_!"

Using a spell he had learnt for Herbology purposes in such a way was not something Harry would have wanted to do, but it did its job, as a gaping wound appeared on the minotaur's chest and forced the beast to stop. The mist that had appeared from nowhere was also making it a bit harder to see.

Perhaps it was time to be a bit creative.

" _Mucus as Nauseam!"_

" _Rictusempra!"_

" _Avifors!"_

" _Verdimillious!"_

The flurry of spells made their work as intended. The Curse of the Bogies was enough to distract the minotaur, while the Tickling Charm had the effect of making the beast contort itself in snorts. The Avifors spell turned a few stones into birds that attacked the minotaur, while the Verdimillious charm was used in a feeble attempt at knocking back the monster.

And then Harry heard it – the sound of fast galloping. And it came accompanied by a shape that appeared from behind the minotaur, as a dark clad rider came from behind the trees and bisected the minotaur with a strange whiteish weapon. The monster burst into golden dust, which scattered into the nightly winds, while the dark horse stopped and turned around, its rider now turned towards Harry, who saw something that terrified him.

The horseman had no head. Or rather, he carried his head in one of his arms.

"What…?" he managed to say.

The headless rider moved his head so it was turned towards Harry, its milky eyes looking directly at the boy. Harry felt paralysed, if in fear or because of something the rider was doing, he did not know.

They stood there for a few moments, observing each other, until suddenly from the mist emerged a coach of dark wood, manifesting behind the horse as if it had always been there. Harry managed to move away as the horse began to walk forward, and stepped back so that he was not run over by the carriage. It stopped right as its door was in front of him, which opened slowly as if it was inviting Harry in. The head of the horseman was turned towards him, as if expecting him to enter the carriage, yet Harry saw no reason to enter.

Yet…

There was something strange… an urge he felt to enter the carriage. It was almost if all reason left him, but Harry turned around to grab his things, only to look back at the open carriage and seeing that they were somehow already inside, with even Hedwig looking as bewildered as it was possible for an owl inside her cage. Taking a step forward, one feet after the other, Harry climbed onto the carriage, the door closing behind him. Even inside, he felt a strange and rather eerie calmness, and the boy could only sit down

Harry heard felt the carriage beginning to move and the sound of the horse's galloping could be faintly heard through the coach's noise. Harry looked at Hedwig, who was now seemingly asleep, and he too began to feel unusually tired. Leaning his head against the carriage's wall, Harry closed his tired eyes, and in mere moments the young wizard was in a deep sleep.

* * *

When Harry regained consciousness, he still felt the carriage moving. Opening his eyes, he saw that the inside was illuminated by the outside light, and the young wizard looked out of the small window to see the coach approaching what seemed to be a town. As it got closer, the carriage seemed to get slower, until it eventually stopped before an archway in the walls that gave entrance into the town.

The door opened on itself, and Harry warily stepped outside, his feet landing on a stone road. He looked behind, and saw that the carriage was gone, his luggage and Hedwig's cage next to him, and the horseman was left only with the horse. He gave one final look at Harry, before putting his head away and riding away into the deep mist, disappearing from sight before the mist dispersed.

"Well, well… a new arrival. And one brought by the Dullahan, no less…"

Harry looked at the source of the voice, and saw only a black cat with a small patch of white fur on its chest sitting on a stone bench.

"Y-You… talked?"

He was imagining things, wasn't he?

"Talked? Shouldn't I?"

Nope, definitely not imagining things.

"You're a cat," stated Harry, his voice expressing how surreal this whole thing was.

The cat huffed. "A cat. I'm not 'a cat' as you put it. I am the cat. Their king, in fact," he declared. "You mortals call me the Cat Sidhe."

Harry had never heard such a name in his life.

"This is the part where you introduce yourself."

Harry had the decency of looking a bit sheepish.

"I'm Harry. Harry Potter."

"The wizard?"

Harry nodded, a bit surprised at being somewhat recognized.

"Huh. I've heard whispers of your name, but never paid much attention to them."

There was a moment of silence, quickly broken by Harry. His need for answers was too great.

"So, why am I here?"

It was the cat's turn to look sheepish. "Ah… well… that is not for me to say. Such task befalls upon the lady of this isle."

Harry looked behind him, and saw a cliff on the distance, beyond it an endless and misty sea.

"This is an island?"

"Now that depends on your definition of island," said the Cat Sidhe. "Which is to say, yes and no."

Harry was just even more confused. "How can this be and not an island?"

"It's difficult to explain. But any questions you might have can be answered later. For now, you need to come with me."

But Harry looked with suspicion at the cat. "Where?"

"To meet the queen of this place," said the cat, glancing back at Harry. "She meets all new arrivals to the island. And you don't want to be late."

"Late? She doesn't even know I'm here!"

The Cat Sidhe scoffed. "If you're here, then she already knows of your arrival. Come on, follow me and bring your baggage."

Considering he had been delivered to a strange place with no explanation of why he had been taken there, Harry guessed that following the talking cat was perhaps his best chance of getting some answers. Taking hold of his trunk and Hedwig's cage, Harry followed the cat as he entered the town. The architecture was strange, Harry had to say. A mixture of Greek or Roman with Gothic and Tudor. It was charming, in its own weird way.

There were no people in the narrow streets, which Harry found odd. If anyone lived here, then perhaps they were still asleep.

Eventually they reached a palace, guarded by moving statues of oddly dressed knights. Taken inside, Harry followed the Cat Sidhe down a hallway of marble until they reached a set of golden doors.

"Potter," spoke the fairy. "For your sake and mine, don't mention Merlin around her, yes?"

Harry looked at the cat with confusion, but nodded. "Okay…"

The Cat Sidhe raised his right paw and touched the door twice, as if through magic, they opened slowly, revealing a large terrace overlooking the sea.

"Your majesty, I bring the new arrival," declared the fairy.

And before him was a woman whose presence was as awe inspiring as it was intimidating. She emanated royalty as the sun emanated light, and her hand grasped a serpent-entwined staff whose emerald eyes seemed to gaze directly at him.

And yet, Harry had seen her before. Not in person, but as a figure in one of his Chocolate Frog cards.

"Allow me to introduce you to the queen of Avalon, Morgana of Trevena."

To say he was bewildered was an understatement.

"Morgana?" he asked. "As in, Morgan le Fay?"

As far as he knew Morgana had been a dark witch who lived many centuries ago. At least according to the Chocolate cards.

The sorceress smiled.

"One of my names, but alas, a wrong one," she said. "I'm not a fairy, after all. But yes, I am that Morgana. Now tell me, young one, what happened before you arrived here?"

"I was attacked by a minotaur. I tried to use magic against it, but then something came and killed it."

"The Dullahan," said Morgana.

Dullahan. So that was what the headless horseman was called.

"He protects Britain against foreign monsters. He must have sensed the man-bull and came to deal with it. And then he found you as well," explained the sorceress-queen, to which Harry nodded.

"Then he brought me here. Why?"

That was the crux of the situation.

"You are here because you are a demigod," answered the sorceress.

"Demigod?"

"Half-god. Half-divine. One of your parents was mortal, while the other was a god. Or a lesser spirit."

"One of my… none of my parents were gods!" he protested. "They were wizards, but not… gods. I've seen them before. My grandparents too!"

Even if it had only been because of the Mirror of Erised, Harry had indeed seen his grandparents before. He knew the family of his mother and that of his father. People always compared him to James Potter because of his appearance, and claimed he had his mother's eyes.

To Morgana however, this was not the first time such a situation had come up. And she knew it wouldn't be the last.

"I cannot claim to know what happened with your parents. I do not know if one was not faithful, or if your divine parent disguised themselves as one of your mortal parents," she spoke gently. "But the matter stands Harry, that you would have not been brought here or attacked by the minotaur if you weren't a demigod."

Harry felt conflicted. The reality of either James or Lily Potter not being one of his parents troubled him to no end. The two had died for him, and now he was being confronted with the possibility that one of them was not really his father, or mother.

Yet, part of his knew that Morgana spoke the truth.

"Now, I have to discuss your claiming ceremony with the cat," said Morgana, "Could you please wait outside for a moment?"

"My claiming ceremony?"

Morgana nodded. "The Cat Sidhe will explain it to you."

Harry was curious, but he nodded and walked back into the corridor, the doors closing behind him as the queen of Avalon and the king of the cats glanced at him.

"You felt it, didn't you?" he asked. "How little mortality he has. The boy's no demigod."

Morgana frowned and sighed. "Diagenesis. It is the only explanation. We have another Maeve in our hands."

The Cat Sidhe approached the sorceress-queen and jumped on top of the balustrade.

"But Maeve was completely ours. The boy is a hybrid. One is ours, and the other is either Greek or Roman," said the fairy, now looking at Morgana. "The question is… who?"

Morgana had her guesses, but she was not about to share them. It was best to let these things reveal themselves. It saved them from a great lot of trouble.

This noon however, they would know at least half of the answer.

* * *

When the Cat Sidhe returned, the fairy told Harry what the young wizard had been expectant to know.

"So… the claiming ceremony?"

The cat nodded. "Right… the claiming ceremony is where your divine parent publicly claims you are their son. Either a god, or one of the lesser spirits, like fairies."

That sounded strange, Harry thought.

"How does it work?" asked the wizard.

"Simply, you climb onto a platform, and the emblem of your parent appears. If they don't have an emblem, then an ethereal apparition of them shows up above you."

"Sounds… easy enough, I guess."

"It is easy. All you have to do is stand there while everyone watches you."

Harry blinked. "Everyone? What you you mean everyone?"

The Cat Sidhe snorted. "It's a public ceremony. People will be watching. What did you expect?"

So, he had to stand on a dais and be claimed by his parent while being watched by a lot of people. That sounded eerily like the Sorting Ceremony at Hogwarts. Harry sighed in resignation. "So, when will it be?"

"Soon enough. At nine, since people usually eat breakfast at eight here."

The fairy closed his eyes for a moment. "A quarter to eight."

Oh goody. One hour to go.

"Well, come along. Let's get you something to eat before the ceremony starts."

At least something good before it, as Harry was admittedly a bit hungry, considering he had ate almost nothing yesterday because of Marge.

* * *

The one hour had gone quickly, and Harry had made little conversation with the Cat Sidhe. Although he was curious about things, the nervousness of the claiming was consuming him. Eventually, he had been brought to a large amphitheatre, in the place of where the stage would be, a large platform with a raised dais stood, and Harry guessed that was where he would be going to.

When he entered the arena, accompanied by Morgana and the Cat Sidhe, there were already many people inside, waiting for the event to begin. Mostly children and teenagers, but quite a few adults could be seen, as well as other creatures, some humanoid.

"See that platform?" asked the Cat Sidhe, to which Harry nodded. "When I say, you have to go to it, alright?"

Harry nodded, and watched as Morgana walked towards a raised platform amongst the audience seats, where a stone throne stood. She sat down, and silence fell upon the amphitheatre.

"We stand here gathered for the claiming ceremony of one that joins us!" spoke Morgana, before her eyes fell upon Harry, who gulped in nervousness. "One who until today was ignorant of his true parentage. Regardless of whom his true parent is, you shall welcome him as one of you, and shall be welcome to this isle for as long as he obeys the ancient laws of the gods."

There were a few whispers, but nothing that Harry couldn't ignore. The need for this whole thing to be over was becoming greater with each passing second.

"Harry James Potter, step forward onto the dais!"

It had been the Cat Sidhe who spoke, his voice booming across the amphitheatre despite his relatively small size.

Swallowing the saliva that had been building up, Harry turned and looked at the dais. Slowing walking up, he began to hear the whispers rise, until he finally reached the dais. Turning around, he looked at the many who were gathered, and felt the same he had those years ago before he had been sorted into Gryffindor.

Suddenly there was a bright light, and below him a blue emblem appeared on the pedestal – an hourglass above a sun and a crescent moon.

There were a few gasps and a deathly silence fell over the theatre. Even the Cat Sidhe's eyes were wide open in shock.

"It is determined!"

It was Morgana who broke the silence, which provided a token relief for Harry.

"Antipatros. Lord of the Tides of Fate, Master of the Cycle of Life and Death, King of the Living and the Dead, the Bane of Cernunnos and Anann," spoke the sorceress-queen. "Hail Harry James Potter, firstborn son of the God of Time and of the Underworld."

And as everyone around him knelt, Harry knew that his life had taken an irreversible turn.

* * *

_**The Tome:** _

**Dullahan** \- a fairy with the form of a headless horseman. A servant of the god Aethon, the protector of heroes, the Dullahan has the task of protecting the British Isles against incursions of foreign monsters, and to bring any demigods he finds to the isle of Avalon. He fought against the Tuatha Dé Danann during the second rebellion.

 **Morgana** – an immortal and powerful sorceress who is the Queen of Avalon. She is the daughter of Gorlois of Trevena, Duke of Cornwall, and Igraine. She married Urien, the king of Rheged, and had a son with him called Owain. Through her mother, she is a granddaughter of Mordeleg, the Britannic god of medicine and prophecy.

 **Avalon** – also called Emain Ablach, the isle of Avalon is a plane of the Otherworld. It was here that the mortally wounded Arthur Pendragon was brought after his battle against Mordred.

 **Antipatros** – part of the second generation of the Dekatriatheón ("thirteen gods"), he is the Britannic god of time, youth, life, death, fertility, wealth, and the Underworld. He is the son of Antiochos Theos and Cordelia, the king and queen of the gods. He fought against the Tuatha Dé Danann during the second rebellion.


End file.
